Conventionally, it is known that efficient heat transportation becomes possible by using latent heat materials.
Also, a heat transportation device for transporting heat by a heat transport medium in a heat transportation circulatory system connected to a heat source by using a fluid containing latent heat materials as a heat transport medium (patent literature 1), and a high temperature region cooling device using a slurry of latent heat material suspension (patent literature 2) is known.
In the heat transportation device mentioned above (patent literature 1), as a fluid that includes a latent heat material (a latent heat storage material) to be used as a heat transport medium, a fluid wherein a fine solid particle of a latent heat material that changes its phase from solid to liquid by melting at a desired temperature (a phase change temperature) being dispersed in a vehicle such as water is used. As a latent heat material, octacosane (C28H58 a melting point 61.5° C.). and so on are used when the desired temperature is set at 60° C., for example. Also, it is disclosed that a surfactant such as polyethylene glycol and stearyl ether for adding hydrophilicity with water and a dispersant such as sodium alkyl benzene sulfonate for improving dispersion stability of fine latent heat materials are added to a latent heat material to make a heat transport medium using emulsion made by dispersion of these agents in water. Furthermore, it is shown that the microencapsulated latent heat material can also be used as a heat transport medium and material systems wherein shells made of rubbers, plastics, metals and so on are filled with latent heat materials such as magnesium chloride, sodium chloride, paraffin, naphthalene and so on are exemplified as such. (Refer to paragraph 0009 in patent literature 1)
Also, in the high temperature region cooling device mentioned above (patent literature 2), it is described that the phase transition temperature whereat a high temperature heat source and a low temperature heat source exchange heat by utilizing a latent heat material being in a higher temperature region in the form of suspension and slurry in a heating medium, the scope of applicability can be extended to objects in a higher temperature region, to employ paraffin, hydrates and microencapsulation thereof all being suspended in the heat medium, and the latent heat materials are to be selected corresponding to their phase transition temperatures. Also, it is shown that the latent heat materials need to exist in a solid state when the heat medium absorbs heat from high temperature heat source for utilizing the phase transition of the latent heat materials, and that the solid state latent heat materials included in the heat medium are preferably made into particles to be easily suspended in solvents so that the transportation thereof can be easy. (Refer to paragraphs 0007 and 0010 in patent literature 2)
On the other hand, micro spherical containers of particle sizes from several μm to several hundred μm with outer shell of about 1 μm thickness capable of liquid or solid inclusion are called micro capsules. Especially, hollow silica microcapsule is an excellent material hardly affecting organisms and environment in negative way.
As a manufacturing method of hollow silica microcapsules, for example, a method to have silica precipitate on oil drops and organic polymer particles that form emulsion or particulates in water, to manufacture materials in core and shell structures and then to have the oil drops and polymers be removed by calcination or solvent extraction making the particulates hollow, is known. Specifically, it is known that the manufacturing method of hollow silica micro capsules consists of the following three processes, namely, the first process wherein a W/O type emulsion is obtained by mixing an organic solvent and a surfactant into an aqueous solution containing at least one kind of alkali metal silicate, the second process wherein hollow silica micro capsules are formed by mixing an aqueous solution of a compound being at least one kind selected from a group consisting of inorganic acids, organic acids, ammonium salts of inorganic acids, ammonium salts of organic acids and carbonates of alkali metals, and also capable of forming a water insoluble sediment by reaction with alkali metal silicate in aqueous solution with emulsion obtained in the first process, and the third process wherein the hollow silica micro capsules thus formed are washed in turn with alcohol and water, and then dried. (Refer to patent literatures 3˜9, for example)
The surface of the hollow silica microcapsules obtained by the manufacturing method mentioned above possesses micro pores and the hollow silica microcapsules are widely used in fields such as cosmetics, medicines, agricultural chemicals, catalysts, fibers, printings, films and so on.